The above-mentioned flotation processes are based on the use
of the fatty acid or tall oil type of collectors, which require the
use of divalent or trivalent activator cations. The presence of
activator ions makes the process sometimes difficult to control
because of the necessity to maintain a proper balance between
the amounts of collector and activator added. For instance, an
excessive use of activators can induce coagulation of the clay
particles and makes the separation difficult. Further, activators
may also cause the flotation of the clay particles themselves
rather than the colored impurities, resulting in a poor separation
efficiency and a loss of clay recovery. It is, therefore, desirable
to have a collector for colored impurities that does not require
activators.